The present invention relates to a cross connection structure for dual high-pressure discharge lamp banks and transformers thereof. With the cross connection structure, high-pressure discharge lamps in the same lamp bank could be maintained at a voltage having the same phase with a small potential difference among them. The problem of mutually repulsion among the lamps in the same lamp bank is eliminated to ensure safe use of the lamps.
FIG. 1 shows a conventional manner for connecting dual high-pressure discharge lamp banks to transformers thereof. A first high-pressure discharge lamp bank LP1 includes a plurality of high-pressure discharge lamps LP11, LP12; and a second high-pressure discharge lamp bank LP2 also includes a plurality of high-pressure discharge lamps LP21, LP22. In the illustrated drawing, only two lamps are shown for each lamp bank. The high-pressure discharge lamps in the same lamp bank correspond to one transformer. A first transformer T1 corresponded to the first lamp bank LP1 is connected at two outputs at a secondary side thereof to two lamps of the first high-pressure discharge lamp bank. That is, the first transformer T1 has a first output T11 connected to a high-pressure discharge lamp LP11, and a second output T12 connected to another high-pressure discharge lamp LP12. The lamps in the second high-pressure discharge lamp bank are also connected to one transformer in the same manner. That is, a second transformer T2 is connected at two outputs at a secondary side thereof to two lamps of the second high-pressure discharge lamp bank LP2. More specifically, a first output T21 of the second transformer T2 is connected to a high-pressure discharge lamp LP21, and a second output T22 of the second transformer T2 is connected to another high-pressure discharge lamp LP22 in the second lamp bank LP2. On the other hand, primary sides of the transformers T1 and T2 are connected to drive circuits 1 and 2, respectively. And, the drive circuits 1, 2 are connected via a signal line 3 to work synchronously.
The above-described connection between dual high-pressure discharge lamp banks and transformers thereof has the following drawback that two lamps in the same lamp bank separately receive from two outputs at the secondary side of the same transformer positive and negative voltages having the same magnitude but reverse polarities. For example, the lamp LP11 in the first high-pressure discharge lamp bank LP1 receives at a certain time point a positive voltage from the first output T11 of the first transformer T1, while another adjacent lamp LP12 in the same lamp bank LP1 receives at the same time from the second output T12 of the first transformer T1 a negative voltage having a phase reverse to that of the positive voltage received by the lamp LP11. The high-pressure discharge lamps in the same lamp bank are very closely arranged, and there is an extremely large potential difference between two adjacent lamps. For example, in the case each of the high-pressure discharge lamps has a voltage of 500V, there will be an instantaneous maximum potential difference as high as 1000V between the positive and the negative voltage of two adjacent lamps. The closely arranged lamps in the same lamp bank and the extremely high potential difference between two adjacent lamps result in noises and mutual interference of these lamps with one another. The same situation also occurs in the second high-pressure discharge lamp bank LP2.
A primary object of the present invention is to provide a cross connection structure for dual high-pressure discharge lamp banks and transformers thereof to eliminate the drawback existing in the conventional connection manner, so that all high-pressure discharge lamps in the same lamp bank are maintained at a voltage having the same phase without the problem of mutual repulsion between two adjacent lamps.
To achieve the above and other objects, each high-pressure discharge lamp bank includes a plurality of high-pressure discharge lamps, and each transformer includes two outputs at the secondary side. First outputs of all transformers are separately connected to the high-pressure discharge lamps in a first lamp bank, while second outputs of all transformers are separately connected to the high-pressure discharge lamps in a second lamp bank. In this manner, all the high-pressure discharge lamps in the same lamp bank are maintained at a voltage having the same phase with a small potential difference among them. The lamps in the same lamp bank would not mutually repulse and can therefore be safely used. The problem of mutual interference due to noises caused by voltages of different phases and big potential difference can also be avoided.